Hydraulic circuit



Sept. 16, 1941. B. WELTE HYDRAULIC CIRCUIT Filed April 22, 1938 5 Sheets-Sheet l INVENTOR ,Befiealbf Welie.

Sept. 16, 1941. B. WELTE HYDRAULIC cmcurr Filed April 22. 1958 5 Sheets-Sheet 2 m W u 1 e a z A ORNEYs.

Sept. 16, 1941. B. WELTE HYDRAULIC CIRCUIT Filed April 22, 1938 5 Sheets-Sheet 3 INVENTOR 3&1764622 Wezz t- ORNEY Sept. 16, 1941. B. WELTE 2,256,332

HYDRAULIC CIRCUIT Filed April 22, 1938 5 Sheets-Sheet 4 INVENTOR 2:17:4 'ci Welfe.

TORNEY I i l Sept. 16, 1941. B, WELT: 2,256,332

HYDRAULIC CIRCUIT Filed April 22, 1938 5 Sheets-Sheet 5 INVENTOR Zezrea'kl 14 822 8- ATTORN EY Patented Sept. 16, 1941 UNITED STATES PATENT 1 OFFICE HYDRAULIC CIRCUIT Benedict Welte, Berkley Mich assignor to Coloration of Delaware nial Broach Company, Detroit, Mich, a corpo- Application April 22, 1938, Ser ialNo. 203,654

20 Claims.

having three hydraulic cylinders which are requiredto move through a continuous cycle; to provide a hydraulic circuit control for three hydraulic cylinderswhere two of the cylinders may be for broaching rams and the third cylinder for moving the work supports toward and away from the respective broaches; to provide a positive interlock between the movements of the cylinders which makes it impossible to move either of the breaching cylinders simultaneously with the movement of the Work shifting cylinder;

to provide an arrangement in which the hydraulic cylinders of the main circuit are automatically pre -filled to compensate for any loss of oil; to provide an arrangement in which the pre-fill of the two main cylinders is completed before movement of the third or work shifting cylinder is possible; to provide a quick and positive stop of all moving members in case of emergency; to provide an arrangement in which the moving parts may be returned to starting position following an emergency stop, and to provide an arrangement in which the last moving part is the first to return to its starting position after an emergency stop followed by reversing.

An illustrative embodimentof this invention 9 is' shown in the accompanying drawings, in

which: 7

Figure 1 is a diagrammatic view of the improved hydraulic circuit, and various control valves therefor;

Figures 2, 3 and 4 show the improved hydraulic circuit of Figure 1, but with the valves in each case in the positions they assume during different portions of the cycle of operation of the machine;

Fig. 5 is a fragmentary section taken along the line 5-5 of Figure 1; and

Fig. 6 is an enlarged, sectional, detail view, showing how the lever 99 may be released from connection with the control plungers I02.

In the drawings, which are somewhat dia-.

grammatic, a main hydraulic fluid pump 5 and secondary hydraulic fluid pump 6 are driven by an electric motor I. Fluid is supplied to the 9 pumps from a reservoir 8 through an intake conduit 9 having branches l0 and H to the pumps 5 and 6, respectively.

The main fluid pump 5 discharges through a conduit [2; a pressure relief valve [3, and conm and 4 cylindrical, axially spaced; lands I9, 20, 2|, 22,

and 24 joined by reduced neck portions which "permit the passage of fluid axially within the limits-of any two lands. The interior wall of the bore I! is provided with axially spaced, encircling grooves or ports I5, 25, 26, 21, 28, 29 and 30, which are positioned so as to be controlled by the lands of the spool [8.

One end of the valve spool I8 is formed to provide a spring centering means comprising an integrally formed, axially extending rod 3|, surrounded by a helical compression spring32, the opposite ends of which bear against washers 33 and 34 which are slidable on the rod 3|. The outer end of the rod 3| has a set collar 35 rigidly fixed thereon, washers 33 and 34 and collar 35 are all of slightly smaller diameters than the bores in which they fit with the result that oil may flow around them. In addition, washers 33 and 34 are provided, respectively, with auxiliary holes 33A and 34A adapted to permit the flow of oil through them from one side of the washers to the other. The casing of the valve i6 is provided with a shoulder 36 against which the floating washer 34 abuts, and an end wall plate 31 against which the floating washer 33 abuts, after the usual manner of spring centering devices of this character. Ports 25 and 28 of the main control valve l6 are connected by lines 25A and 28A to a fluid return line 55, and port 29 is also connected to the return line 55 through a by-pass valve 29A, which operates to permit flow from port 29 to line 55 when the value. The by-pass valve 29A may be of any conventional form, such as that illustrated and described in connection with valve 4! hereinafter. A

The ports 26 and 21 of thevalve l6 have primary pressure line conduits 38 and 39 communicating therewith, hereinafter referred to as the primary circuit, which conduct fluid under pressure to and from a pair of vertically disposed hydraulic breaching tool or work performing I through a by-pass valve 41 and line 48 to a pressure'relief valve 49, thence through a line 58 to a fluid pressure operated four-way secondary control valve 5|. The relief valve 49 is connected to a fluid return line 54 by a line 49A. The secondary valve 5| has pressure working lines 52 and 53 connected thereto, hereinafter referred .to as the secondary circuit, and a fluid return line 54, which connects with a fluid return line 55. The line 55 leads to and discharges into the tank orreservoir 8.

The function of the by-pass valve 41 is to prevent the flow of fluid under pressure to line 48 until the pressure in lines 44 and 46 reaches a predetermined value, as pointed out hereinafter. The valve 41 is a conventional form of pressure responsive by-pass valve having a spool 41A adapted to control communication between ports connected to lines 45 and 48. The spool is normally urged toward the right, as viewed in Figure l, by-an adjustable spring 41B, in which position the lefthand land on the spool closes communication between lines 45 and 4 8. The valve body, however, contains a small passage 41C connecting the port associated with line 45 line. 45 to line 48. When the pressure drops below that value, the spring closes the valve.

The valve 49 is a conventional form of pressure relief valve which functions to connect lines 48 and 50 to the low pressure tank, or reservoir, 8 under certain conditions.

the right, as viewed in Figure 1, to close the port in communication with the discharge line 49A.

'This spool is normally urged in a direction to close the port associated with line 49A by a I spring 490. The spool is provided with a piston 49D which fits the bore of the valve body and which is subject at one side to the pressure in the lines 48 and 58. The piston 49D, however,

The valve is pro-- .vided with .''a spool 49B adapted when it shifts to tion between lines 48 and 50, and the pressure at the righthand side of the piston 49]) is balanced by reason of the fact that the same pressure is transmitted through the bleed opening 49E to the opposite side of the piston. Undernormal operating conditions, the pressure in lines 48 and 50, which pressure acts through the bleed opening 49E, is insuflicient to lift the spr pressedball valve 49G oif its seat. However, if

the pressure in lines 48 and 50 exceeds a pre-.

- line 49A. This causes a drop in pressure at the spring, the valve opens and permits flow from lefthand side of the piston 49D, because the flow through the bleed opening 49E is restricted. As a result, the pressure acting on the righthand side of piston 49D opens the valve and vents the lines 49 and 50 to the reservoir 8. The same result may be effected at any time by connecting the pilot line 200 to the rservoir, since this likewise lowers the pressure at the lefthand side of piston 49D causing the valve to open the port connected with the discharge line 49A.

The valve 5| is a conventional pilot operated four-day valve having a valve spool provided with three lands adapted to control the ports in communication with thelines 50, 52, 53 and 54. When the spool is in the position shown in Figure lof the drawings, free flow is permitted from the pressure line '58 to the line 52 through the space between the lefthand and central lands on the spool. At the same time, return flow is permitted from line 53 to line 54 through the space between the central and righthand lands on the valve spool. When the spool is in its lefthand position, free flow of pressure is permitted from line 58 to line 53 through the space between the central and righthand lands on the spool. .and at the same time return flow is'permitted from line 52 to line,54 through thespace between the ,central and lefthand lands on the spool. The

position of the valve, spool is controlled at all times by pilot pressure admitted through lines 282 and 203 to the ends of the spool bore. In the position shown in Figure 1, pressure is applied through'line 202 to shift and hold the spool to .the right, and line 283 is connected to the reservoir.

g The secondary'circuit lines 52 and 53 are connected to axially aligned, integrally formed, hellow piston-rods 56 and 51 of a work moving hydraulic cylinder 58 which is disposed transversely with respect to the work performing cylinders 40 which serves normally to balance the pressures on opposite sides of the piston. The lefthand end of the spool 49B fits-in a spring bore of the housing, and the space at the lefthand side of the piston 49D is adapted to be connected to this spring bore by a passageway containing a springpressed ball valve 49G. The valve 49G normally closes communication through this passageway. The spring bore in the body is also connected to the discharge line 49A through a. bore 49F through the spool 493. The space within the valve body at the lefthand side of the piston 49D is also connected to a pilot line 288. The operation of the valve is as follows J -Spring 49C normally shifts the spool 4913 into a position in which it closes the port connected with the discharge line 49A. When the discharge port is closed, there is free communicaand 4|. The cylinder 58 is adapted to be connected to a pair of work supporting fixtures, or

the like, for alternately moving work toward and away from the broaching or work performing cylinders 40 and 4|. Fluid-from the lines 52 and 53 passes out through apertures 59 and 68 formed in the hollow piston rods 56 and 51, respectively; closely adjacent to a stationary piston 6| upon which is slidable the cylinder 58, it being understood that the piston rods 56 and 51 are the other.

,I'he details of construction of the work moving cylinder .58 and the work performing cylinders 40 and 4|, with the machine in which they are mounted, are shown in the copending joint application of applicant and Albert H. Werden, Serial No. 199,756, filed April 4, 1938, issued De :ember. 17, 1940, as Patent No. 2,225,191, and issigned to the assignee of this invention.

The line 46 carries fluid through a branch line 52 to a control valve, generally designated 63, and through a branch line 64 to a control valve generally designated 65. The control valve 63 is provided with a cylindrical bore 66 in which is axially slidable a valve spool 61. The spool 61 is provided with bore fltting, cylindrical, axially spaced, lands 68, 69, and 1|, connected by reduced neck portions which permit the flow of fluid axially between the lands in the usual manner.

The cylindrical bore 66 has; its interior wall provided with axially spaced, encircling ports 12, 13, 14, 15, and 16, which are positioned soas to be controlled by the lands of the spool 61..- The spool 61 is provided at one end with an integrally formed, axially extending rod 11 which, through a lever 18, is connected to a spring centering device 19.

The spring centering device 19 comprises a collar 80, helical compression springs 8I and 82 which bear against opposite sides of the collar 80 and the respective ends of a stationary housing. The collar 80 is secured to a rod 83 which passes axially through the housing and which is connected to one end of a lever 84, the other end of which is in position to be engaged by depending lugs 85 and 86 carried by the hydraulic cylinder 58. 4

Ports 12 and 16 of the control valve 63 are connected by branch lines 81 and 68, respectively, to a fluid return line.89 which empties into the return line 55, and thence into the reservoir 8.

The control valve 65 is provided with a cylindrical bore 90 in which is axially slidable a valve spool 9| The spool 9| comprises bore fitting, axially spaced, cylindrical lands 82, 93, 94, and 95, which are connected by reduced neck portions in the usual manner. One end of the valve spool is provided with an integrally formed, axially extending rod 96, the outer end of which is pivotally connected to one end of a lever 91, the other end of which is connected to one end of a control rod 98. The other end of the rod 98 is connected to one end ofa lever 99 which is rockable on an axially slidable pivot I00. As

best shown in Figs. 5 and 6, the lever 99, at points equidistantly spaced at opposite points of the pivot I00, is detachably connected to plungers IOI and I02, which are positioned to contact lugs I03 and I65A, carried by the main broaching cylinders 40 and M, respectively, for shifting the plungers to rock the lever 99, and thereby through the links, movethe spool 9I axially in its bore. The lever 99 is normally held in engagement with the plungers IOI and I02 by a compression spring 99A.

It is to be understood that the drawings are diagrammaticto a great extent inasmuch as the elements involved are well known to those skilled in the art. The plunger I02 is shorter than the plunger II, and when the plunger I02 is contacted and moved by the lug I03, the linkage moves to acentral position, at which time both ends of the plunger I0 I protrude slightly beyond the ends of the plunger 1 I02 so that the cam lug I65A may pass by the ends of the plunger I02 but will contact and move the plunger IN to the opposite position.

The lugs I65 and I04 and the plunger .I64 are all in the same vertical plane, which is offset from-a common vertical plane which contains lug I65A, lug I03, plungers IM and I02. The

width of lug I04 and also the length of plunger I64 must be such that when lug I04 comes opposite to plunger I64, it will be shifted to the right an equal amount as it is shown to the left now.

The interior wall of the cylindrical bore 98 of valve 65 is provided with axially spaced, encircling port grooves I05, I06, I01, I08, and I09, which are positioned so as to be controlled by the lands of the spool 9|. The ports I05 and I09 communicate with the fluid return line 39 through lines IIO and III, respectively.

The ports 13 and 15 of valve 63 are connected to lines H2 and H3, respectively, which conduct fluid to and from a control valve, generally designated II4. Control valve H4 is provided with a cylindrical bore I I5 in which is axially slidable a valve spool II6, which has bore fitting, cy-

lindrical, axially spaced landsIIl, H8, H9, and 1 I20 connected by reduced neck portions in the usual manner. One end of the spool H6 is provided with an integrally formed, axially extending rod I2I, the outer end of which is pivoted to the outer end of an arm I22 of a bell crank lever rockable on fixed pivot I23. The other arm, I24, of the bell crank lever is connected to one end of a link I25 by a slot and pin. connection I26. The other end of the link I25 is pivoted to the outer end of an arm I21 which is integrally formed on the lever 91f" The interior wall of the bore II5 of valve H4 is provided with axially spaced, circling port grooves I28, I29, I30, I3I and I32, which are positioned was to be controlled by the lands of the spool H6. The ports I29 and I3I are connected to lines I 33 and I34,-respectively, which lead to a manually operable control valve generally designated I35.

The valve I35 is provided with a cylindrical bore I36 in which is axially slidable a valve spool I31. The spool I31 comprises bore fitting, axially spaced, cylindrical lands I38,- I39 and I40, which are connected by reduced neck portions in the usual manner. One end of the spool I31 is provided with an integrally formed axially extending rod I4I, the outer end of which is rigidly connected to a cross head I42.

The interior wall of the bore I36 of valve I35 is provided with axially spaced, encircling port grooves I43, I44, I45, I46 and I41, which are positioned so as to be controlled by the lands oi? the spool I31. The ports I43 and I41 are con nected to lines I48 and I49, respectively, which join in line I50. The line I50 leads to and con- I ducts fluid to the control valve I6 at the right hand end thereof, the communication being to that part of the valve casing which houses the valve centering means,

The port I of valve I35 is connected to a line I5I which leads to the opposite end of the control valve I6 for carrying fluid into the casing to shift the valve spool I8 to the right therein, as shown in the position illustratedin Fig. 1 of the drawings. The lines I and I5I; lines I33 and I34; and lines I I2 and H3 are hereinafter referred to collectively as the primary pilot circuit.

' The ports I06 and I08 of control valve 65 are connected to lines I52 and I53, respectively, which lead to a control valve generally designated I54 in which is axially slidable a valve spool I". The spool I55 comprises bore fitting, axially spaced, cylindrical lands I56, I51, and I" joined which passes through a spring centering device The cylindrical bore I66 of the valve I54 is provided with axially spaced, encircling port grooves I61, i68, I68, I18, and HI, which are positioned so as to be controlled by the lands of the spool I55.

The port I68 of control valve I54 is connected to the port I38 of control valve H4 by a line I12, and the port I 69 is also connected to the return fluid line 88 by a line I13.

The line I 52 has a branch pre-fill line I14,

, which passes through a check valve H5, and

thence to a line I16, one end of which communicates with the port 88 of valve I6, and the other end of which passes through manifold 43, and thenceto the interior of breaching cylinder 4i above the piston 39A for moving the cylinder upwardly.

The line I53 has a branch pre-fill line I11 connected thereto which passes through a check valve I18, and thence to a line I18, one end of which communicates with the port 281 of valve I6, and the other end of which passes'through the manifold 42 and into the breaching cylinder 48 above the piston 38A, for moving the cylinder upwardly. The lines I14 and I11 are hereinafter referred to as the pre-fill circuit and the lines I16 and I18 are hereinafter referred to as the closed circuit.

Ports I68 and I18 of control valves I54 are provided with lines I88 and I8I, respectively, which communicate with a manually operable control valve, generally designated I82. The valve I82 is provided with a cylindrical bore I88 in which a valve spool I84 is axially slidable. The spool I84 comprises bore fitting, cylindrical, axially spaced lands I85, I86, I81, and I88, connected by reduced neck portions which permit flow of fluid axially within the limits of any two of the lands. One end of the spool I84 is provided with an axially extending rod I88 which is rigidly connected to the cross head I42 so that the spools I84 and I 81 may be moved in unison -manually by a link I88 which is connected to a hand lever I8I.

The interior wall of the bore I88 is provided with axially spaced, encircling, port grooves I82, I88, I84, I85, I85, I81, and I88 which are positioned so as to be controlled by the lands of the spool I84. Port I88 has a line I88 connected thereto which communicates with the fluid return line 88. Port I81 has a line 288 connected thereto which conducts fluid from the relief valve 48. Ports I86 and I82 are connected by lines .28I

and 282 to one of the valve operating ports of the fourway valve ii. The port I84 is connected by a line 288 to the other valve operating port of the four way valve III. The lines 28I, 282, 288, I88, I 8|, I 52 and I88 are hereinafter referred to as the secondary pilot circuit for operating the secondary control valve of the secondary circuit.

In operation, this hydraulic circuit, as heretofore stated, provides control for a, machine having three hydraulic cylinders which are required to move through a continuous cycle. The cylinders 48 and 4| are preferably positioned with their axes vertically and in horizontally spaced parallel relation, and move simultaneously in opposite directions. The stroke of the cylinders is adjustable on the lower end, while on the upstroke the cylinders stop against the piston or any other positive stop which may be provided therefor. After reaching their stopping points, the cylinder 58 is required to make one move, thereby operating a transverse slide or similar mechanism for moving work into position where the cylinders 48 and M operate slides which in turn carry breaching tools, and the cylinder 58 operates a work table with two work holding fixtures in such a way as to put one fixture in cutting position and retracting the other fixtures away from the upgoing broach slide, allowing it .to be unloaded and reloaded with a new work piece.

In Figure 1 is illustrated the position of the parts at the instant of the starting of-the machine. The direction of flow through the lines and valves of the circuit is indicated by the solid line arrows, while dotted line arrows are used to indicate the direction in which pressure is exerted in the absence of flow. In this position of the parts, the hydraulic pump 6 is supplied with fluid from the reservoir 8 through the intake lines 8 and II, and delivers fluid under pressure through the lines 44, 46, and 62 to the port 14 of the valve 63, and through the line 64 to port I81 of the control valve 65. From port I81 the fluid passes axially along the spool 8i into port I86, and thence into lines I52 and into port I61 of valve I54. From port I 61 the fluid passes axially along the spool I55 to port I68, thence into line I88 to port I83 of valve I82. From port I83 the fluid passes axially along spool I84 to port I82, and thence into line 282 which leads to one of the operating ports of the four way valve 5|. Pressure in the line 282 holds the spool of the valve 5| to the right, as viewed in Figure 1 in such a way as to connect the intake line 56 of the valve with pressure linev 52, and at the same time connect line- 58 with fluid return line 54 which empties through the return line 55 into'the reservoir '8. Fluid is supplied to the four way valve 5I through the pressure line 44,

branch 45, by-pass valve 41, line 48, relief valve,

At the same time, fluid from the line I52 passes Into the branch pre-flll line I14, througlr'check valve I15, and thence to the line I16, one end of which communicates with the interior ofthe cylinder 4| above the piston 39A therein, thus insuring the filling of the line with fluid and.

raising of the cylinder 4| to its topmost beginning position. The purpose of this arrangement lies mainly in the period preceding the one shown in Figure 1 of the drawings, and also preceding the movement of valve-5| and cylinder 58 to the positions of Fig. 1. At that time, the. spool I8 of valve I6 is held in its mid-position by the spring 32, and when in that position the land 23 of spool I8 will -be positioned between the ports 29, and 30, which blocks the port 30 from any 'other communication. Thus, fluid entering the line I16 under pressure, moves the cylinder 4| in its top position it not already in that position and supplies any loss of oil past the rings of piston 39A, and the packing glands in the top end of the cylinder during its movement.

As soon as cylinder 56 reaches the position of Fig. 1, fluid from the port 14 of valve 63 was conducted axially of the spool 61 to the port 15, and thence through line II3 to port I32 of valve II4. From port I32 the fluid passed axially along the spool II6 to port I3I and thence through line I34 to port I46 of valve I35. From port I46 the fluid was conducted axially along the spool I31 to port I45, and thence through line I5| to "the left end of the valve I6, thereby moving the I8 and the other parts to the position shown in- Fig. 1, no further flow of fluid can occur in lines 46 and 52. This causes pressure to build up in these lines and consequently in lines 44, 45 and 48 to such an extent that the pressure relief valve 49 opens to the position shown in Fig. 1,- thus venting the pump 6 and pressure line 44 to the tank 8 through lines 49A, 54 and 55. This opening movement of pressure relief valve 49 was the last movement of the parts prior-to their condition illustrated in Fig. 1. Valve 49 serves to limit the pressure which is-built up in the lines in communication with the valve, but when open the pressure is suff cient to hold valve I8 in the position of Fig. 1 against the force of spring 32 so long as line 200 is-closed by the spool of valve I62.

When the spool I3 is moved to the position shown in Figure 1 of the drawings, fluid under pressure from the main hydraulic pump 5 passes through line I2, pressure relief valve I3, line I4, port I5, axially into port 21, and thence into line 39, which leads to the cylinder 4|.

Fluid under pressure from the line 39 will pass through the stationary piston 39A and into the cylinder H at the lower side of the piston, thus moving the cylinder 4| downwardly on its broaching or. work performing stroke. As soon as the cylinder 4| moves downwardly, the lug I55 thereon clears the plunger I64, thus permitting the spring centering device I6I, through the rod I59, to move the spool I55 to its mid-position, at which time the land I56 will cover the port "I and the land I51 will be centered over port I69 but permit passage of fluid thereby due to the notches I55A formed therein, and the land I56 to cover the port I61 and shut off communication therethrough.

Cylinder 4|, in moving downwardly, will force fluid contained above the piston 39A out through the line In; into port so, thence to port 29, and from there into line I19. From line I19 the fluid will enter the cylinder 40 above the piston 38A therein, thus raising the cylinder upwardly as the cylinder 4| moves downwardly. As soon as the cylinder 40 moves upwardly, the lug I03 will disengage from plunger IOI and contact plunger I02, moving it to the right from the position shown in the drawings, and thereby through link 98, lever 91, and rod 96, move the spool 9| to its mid-position. When spool 9| is moved to mid-position, communication between ports I01 and I05 is interrupted, which thereby shuts off further prefill action through the-check valve I15 to the line I16. Spool II6 of valve H4 is not affected by movement of the link 98, lever 91, arm I21, and link I25, due to the slot and pin connection I26, thus leaving the valve in the position shown in the drawings.

Downward movement of the cylinder 4| continues until the lug I65A engages the plunger IOI, at which time the lever 99, and link 98, is moved to the left as shown in Figure 2 of the drawings. When moved to this position, the lever 91, through rod 96, moves the spool 9| to its extreme right hand position, and througharm I21 and link I25, bell crank I22, I24, and rod I 2|, the valve H6 is moved to its extreme right hand position.

Movement of the spool I I6 to its extreme right hand position causes the port I32, which is connected to pressure, to be cut off from port I3| by the land II9 of spool I I6, and at the same time connects the port |3| with the port I30, which, throughline I12, communicates with port I69 of valve I54. From port I69 the fluid is vented through line I13 to the fluid return line 89, thence to'the reservoir 8. This venting of the fluid enables the spring 32 of the spring center means of valve I6 to move the spool III to its mid-position shown in Fig. 2, the fluid from the left end of the cylinder being vented through line I51, port I45, port I46, line I34, port I3I, port I30, line I12, and thence through lines I13 and 89 to the reservoir 8.

In order to let the spool I8 move freely, it is also necessary to connect line I through branch I48, port I43, port I44, line I33, port I29, port I28, line II2, port 13, port 12, line 81 to line 89, and thence to the reservoir 8.

The movement ofthe spool IB to its mid-position serves a two-fold purpose. First, the land 23 is moved in between the ports 29 and 30, thereby shutting ofi communication between the two ports, which arrests, through hydraulic lock the movement of the cylinder 4| Second, the lands 20 and 2| are moved over ports 26 and 21, respectively. Fluid delivered now by the pump 5 is by-passed through the slots 20A and 2IA, respectively, to the ports 25 and 28, thence through the return lines 25A, 28A, and to the reservoir 8.

The work performing hydraulic cylinder 40 should theoretically reach its extreme top position when the lug IA contacts plunger IOI, but in practice two conditions have to be considered. The first is when the cylinder 40 reaches its top position ahead of time. In this case the cylinder 4| continues to move downwardly, and the oil displaced from the cylinder above the piston 39A isforced out through the line I16 into the port 30, but can no longer pass from the port 29 into the line I19 due to the fact that the cylinder 40 has reached its top limit of movement. In such a case the fluid is forced out through pressure relief valve 28A into the retum flow line 55, and thence returned to the reservoir 8.

The second case is where the cylinder 40 lags behind in its movement and does not reach the upper limit of its stroke by the time the cylinder 4,I is forced down to the lower set limit of its stroke. As has been explained before, when cylinder 4I reaches the bottom of its stroke, the spool 9I has men moved into the position shown in Figure 2 of the drawings. Pressure fluid from the port I01 now enters the port I08, and thence into line I53. Port I1I is blocked by land I58 of spool I55, by reason of the spring centering device I'8I which holds the spool I55 in midposition, the land I58 covering the port I1I for the reason that the plunger I64 has not as yet been contacted by the lug I04 of the cylinder 40. Therefore, the only way for this fluid to go is through the line I11, check valve I18, and thence to the line I13, thereby forcing the cylinder 40 on upwardlyto its topmost position, at which time the lug I04 will cam the plunger I54 to the right, thereby forcing the spool I55 to its right hand position, shown in Figure 2.

When the spool I55 is moved to its right hand position, the fluid under pressure in the port I1I will now flow axially of the spool to. port I10, and thence into line I8I which communicates with the port I85 of valve I82. From port I95 the fluid flows axially of the spool toport I34, and thence into line 203 which leads to one of the valve spool operating ports of the four-way valve 5|. The fluid under pressure coming in from the line 203 will now shift the spool in the four-way valve 5| so that fluid entering through the line 50 into the valve will pass out through the line 53 of the secondary circuit, thence to the hollow piston rod 51 and out through the aperture '50 therein into the left hand end of the work moving hydraulic cylinder 58, thereby moving the cylinder 58 to the position opposite to that shown in Fig. 1 with respect to its stationary piston 8|. Figure 2 of the drawings 11- lustrates the position of the valves and parts during movement of the cylinder 58 from its right hand to its left hand position. The cylinder 58 may be connected to'work holding flxtures in such a manner as to move one flxture away from the hydraulic cylinder 4| which has just completed its down stroke and move another work holding flxture into position to be operated on by the hydraulic cylinder 40 when it is next moved downwardly.

It is to be noted that movement of the work shifting cylinder 58 can take place only after both of the work performing cylinders 40 and H have reached their proper positions by reason of the shifting of the spools 9| and I55, which shifting is done only when the cylinders 40 and M have reached their limit positions, at which times the lug I04 or the lug I85 shifts the plunger I84, and either the lug. I 03 or lug I85A shifts the plunger IOI. It will thus be seen that it requires the shifting of both of the spools SI and I55 before reversal of pressure takes place in the pilot lines 202, 203,- which control the four way valve 5|, which in turn controls the secondary pressure circuit comprising the lines 52 and 53. Such an arrangement is very important to the satisfactory operation of a dual ram broaching machine.

As the work moving cylinder 58 moves to the left, as just described, the lug 85 disengages from the upper end of the lever 84 and permits the spring centering device 19 to shift the spool 51 in a left hand direction to its mid-position. The reason for this will be described later. Upon completion of the movement of the cylinder 58, the lug 86 will contact the upper end of lever 84 and move it to the position shown in Figure 3 of the drawings, thereby shifting the spool 81 to its extreme left hand position. When in that position, fluid under pressure from the line 82 and port 14 will enter the port 13, line II2, port I28, and, due to the fact that the spool II5 has been shifted to the right, fluid will flow from port I28 into port I29, thence into line I33 to port I44 of valve I35. From port I44 the fluid will pass axially along the spool I31 to port I43 into line I48, thence into line I50 and into the right hand end of the main control valve I6, thereby shifting the spool I8 to the left, i. e., to the position shown in Figure 3 of the drawings.

When the spool I8 is shifted to the left, fluid from the left end of the valve is vented through line I5I, ports I45 and I46, line I34, to port I3I. The spool H6 having been shifted to the right so that the land H9 is to the right of port I3I, the fluid will flow into port I30, thence to line I12, to port I69 of valve I54. From port I88 it will flow into line I13 to the fluid return line 89, thence through line 55 into the reservoir 8. After spool I8 has been shifted to the left as shown in Fig. 3 valve 49 will open as previously explained to by-pass pump 6 as clearly shown in Fig. 3.

The spool I8 having moved to its new position of Figure 3 of the drawings, fluid under pressure is delivered by the pump 5, through line I2, pressure relief valve I3, and line I4 into port I5. From port l5 fluid will flow axially along the spool I8 into port 28, thence into line 38 of the primary circuit which includes the lines 38 and 39. The line 38 leads to the work performing cylinder 40 which is in its upper position and passes into said cylinder below the piston 38A therein, thereby forcing the cylinder downwardly on its work performing stroke. From here on, the operation of the parts is the same as that heretofore described, with the exception that the cylinders and linkage controls are just the opposite to that hereinabove described. It will thus be seen that there is a positive interlock between the movements of the three hydraulic cylinders 40, 4!, and 58. If either of the cylinders 40 and 4I are not in their extreme position, then the spools 9| and I55 of the valves and I54 will be in their mid-position, whereby the flow of fluid under pressure to the pilot circuit 202. 203, of the four way valve 5| is blocked and no movement of its spool takes place; therefore, no change in the position of work moving cylinder 58 is possible.

Furthermore, when the cylinder 58 is away ing the spool therein. The lands 68 and 10, however, have notches 89A and 10A, respectively, which connect the ports 13 and 15 with the lines 81 and 88 through the respectively adjacent ports 12 and 18. This will equalize any difference of pressure which might exist in the lines I50 and I5I and thereby enable the spring centering device of the valve Hi to centralize the spool l8,

which thereupon blocks movement of the cylinders 40 and 4| by reason of the land 23 of spool I8 moving in between the ports 29 and 30, while at the same time permitting fluid from the pump 5, lines I2 and I4, to be vented by by-passing through the notches 20A and 2|A, and thence to the return lines 25A and 28A to the return line 55.

During long periods of idleness, it may be that the closed circuit comprising the lines I16 and I19 have lost large amounts of fluid. For instance, consider the situation when the machine is set at full stroke. The various parts have just reached the position shown in Figure 1 of the drawings and the motor is shut oil so that the pump comes.t rest before any movement of the spool in the four way valve has taken place. It is further assumed that the machine is now allowed to rest for a length of time during which the cylinder 4| sinks down a considerable distance from its top position, but not so far, as to make the lug I65A contact the plunger IOI.

Now-it is assumed that the motor is turned on again and fluid from the pump 6 flows under pressure through the lines 44, 46, and 64 to the port I01, thence to port I06, line I52, line I14, check valve I15, to line I16. From line I16 the fluid will flow into the cylinder 4| above the piston 39A, thereby-raising the cylinder upwardly to its top position This is made possible by reason of the spool I8 being held in its mid-position by the spring 32 of the spring centering device, and the land 23 shutting off communication between the ports 29 and 30. As the cylinder 4| is thus raised to its top position, fluid is forced out through the line 39 from the under side of the piston 39A and flows through the line 39 into port 21 through the slots 2IA in land 2| to the port 28, and thence through line 28A to return fluid line 55 which leads to the reservoir 8.

During all this time no fluid is admitted to four way valve 5| until the prefill action brings the cylinder 4| to its top position where the lug I65 cams the plunger I64 to the left against the spring centering device I6I, and thereby shifts the spool I55 to the position shown in Figure 1 of the drawings. When shifted to this position, fluid from port I61 will pass axially to port I68, and thence to line I80 which leads to port I93. From I93 the fluid will flow axially of the spool I84 to port I92, and thence to line 202 of the pilot circuit which operates the spool of the four-way valve 5|.

Shifting of the spool in valve 5| permits fluid under pressure from the pump 6 through lines 44, 45, by-pass valve 41, line 48, pressure relief valve 49 and line 50 to enter the line 52 of the secondary circuit, and thence into the right hand end of th cylinder 58 which moves the cylinder to the right, as shown in the drawings,

Consider the machine when the cylinders 40 and 4| are in the position shown in Figure '1 of the drawings, and the work moving cylinder 58 is in its extreme left hand position, and the spool in the valve 5| has been shifted preparatory to the cylinder 58 moving to the right. It is assumed now that the motor 1 is shut off and the 1 machine not used for a considerable length of time. The cylinder 4| under the influence of gravity may sink down from its top position. This creates a hazard, as tools mounted on the slide driven by the cylinder 4| might interfere with any fixtures which would be carried into position in relation to the cylinder 4 I, if it would move as the cycle demanded- Now. upon restarting the motor 1, fluid delivered by the pump 6 will flow first through the lines 44, 46, and 64, ports I01 and I06, line I52, line I14, check valve I15 to line I16, and thereby replenish the fluid on top of piston 39A of cylinder 4|, and thereby lifting the cylinder 4| back to its top position.

The cylinder 58 will not move during this prefill action because the by-pass valve 41 is set at v a sufiiciently'high pressure so as to not allow any fluid to flow through it until after the cylinder 4| has reached its top position, at which time further flow through the line 46 is resisted, and the valve 41 is forced open, thereby permitting fluid to flow through the lines and thus resume the normal cycle of operation.

It is to be further noted that fluid under pressure in the line 46 passes through line 62 into port 14, port 13, line II2, to port I28 of control valve I I4, at which point it is blocked due to the land II8 being in position between the ports I28 and I29. Also, the fluid passing through the line 64 to port I01, port I06, line I52, to port I61, is also blocked by reason of the fact that the spring centering device I6| has moved the spool I55 to the right to its mid-position immediately upon the lug I65 disengaging from contact with the plunger I64.

Considering the machine in a position where the cylinders 40 and 4| are in the position as shown in Figure l of the drawings; the cylinder 58 has started out on its trip to the right and the motor 1 has been shut off. It is assumed that after the cylinder 4| has left it' top position, the motor 1 is turned on again. As heretofore explained, the by-pass valve 41 will prevent any flow of fluid to the four way valve 5|, and cylinder 58 until the prefill action is complete. The cylinder 58 being away from its end position, the spool 61 will be in mid-position, thereby preventing any flow of fluid from the port 14 to either of the ports 13 or 15. Fluid is thus blocked from the line 62 and forced to the line 64 and thence to the prefill circuit.

Consider now the same case of the top cylinder 4| dropping during idleness, but with the machine set at less than full stroke. The difference in this case is that the cylinder 40 is also afiected by gravity, and will lose position. In such an instance, no interference between tools and fixtures and work pieces will take place because gravity will carry the cylinder 40 down" away from the tools. Therefore, it is not necessar to make provision to correct position of cylinder 40 before resuming the normal cycle of operation. Advantage has been taken of this fact. The prefill action through check valves I15 and I 18 is controlled through the valve 65. Prefill is started at either extreme position of the spool 9| and shut off in its center position. Now the ascending cylinder 40 will shut oif this prefill by centering the spool 9| through the plunger I02, link 98, lever 91, and rod 96. The dropping of cylinder 40, however, will not affect the position of the spool 9| because the centering action is caused in this case not by an automatic centering device, but by mechanical linkage which is only effective in one direction.

Considering now the case where the machine being set on part stroke of cylinders .40 and 4| is allowed to stand idle, that cylinder 4I sinks to a position where the lug |65A is below the plunger IOI. In this case the circuit will not automatically correct the position of the cylinders,

and a manual prefill has to be used. As shown position, shown in dotted outline.

' munlcate through port I45, slots 99 is pivoted on an axially slidable shaft I00, and

this shaft can be moved axially to the right, as

viewed in Fig. 6, against the action of spring 99A whereby it is disengaged from the plungers |I and I02, but maintains connection with the link 98. Now, by turning this shaft I00 manually, the spool 9| may be shifted to either extreme position, thereby admitting fluid under pressure from port I01 to either port I06 or I08 and thereby raising either the cylinder 40- or 4| upwardly at the will of the operator until one of the lugs I03 or I65A gets above the plunger |0|, from which point on, the circuit takes care of any further movement. I v The above described disengagement of the lever 99 from the plungers IN and I02 is provided to make the manual Prefill independent of the position of the plungers IOI. and I02, inasmuch as they may become locked by being contacted simultaneously by the lugs I03 and I65A. No in- .by-pass valve 41. Furthermore, the cylinder which was originally in the top position will always be able to return to its top position without interference because the position of cylinder 58 must have been such that the cylinder 4| could sink down without interfering with fixture controlled by the cylinder 58.

With respect to the stopping of all moving' members in case of emergency, or the like, such functioning is controlled by the manually operable valves I and I82, the spools I31 and I84, respectively, of which are rigidly connected to a cross head I42 which in turn i connected through the link I90 to a manual control handle I8I. In order to stop the operation of all parts of the machine, the lever |9| is moved to the center This causes the spools I31 and I84 to move to their center position. The land I39 of spool I31 will now stand midway over the port I45, and the land I40 will be midway over the port I41. Now the pilot line I5I of the main control valve l6 will com- |40A',p6rt 41 and line Me with pilot line I at the other side of the spool I8, thereby balancing hydraulically regardless of pressure conditions in the ports I44 and I46, and allowing the spring 32 to move spool I8 to its mid-position, which, as heretofore pointed out, hydraulically locks cylinders 40 and 4| by blocking communication between the ports 29 and 30, with the land 23, while at the same time allowing fluid delivered by the main pump 5 to be by-passed through the slots 28A and 2IA. This stops the movements of the cylinders 40 and 4| under anycondltions, and vents the pump 5.

The mid-position of thespool I84 provides communication between ports I91 and I98, and allows fluid to 'flow from pressure relief valve 49 through the line 200 to port I91 axially along the spool to the port I93, and thence through line I99 to the fluid return line 89, line to reservoir 8. Due to the particular construction of the valve 49, which construction constitutes no part of the present invention, unrestricted flow through the line 200 will cause the relief valve 49 to allow fluid to be by-passed through the line 49A to line 54, thence to line 55 and to the reservoir 8 at a pressure much lower than necessary I39A, slots to move the cylinder 58 and thereby stop its motion immediately.

After the machine has been stopped by moving the manual control handle I9| to its center position, either by reason of emergency, or otherwise, it may then be necessary to reverse the movements of all of the parts and return them to the positions from which they started, and from there again start out in the normal cycle of operation. Assume that the machine is in the position shown on the drawings and that the cylinder 4| ha started down on'its work performing or cutting stroke, it being assumed that this cylinder is carrying a broaching tool and on its down stroke will perform a breaching operation on a work piece clamped on a fixture which is held in position in certain relationship to the broaches or other tools carried by the cylinders 40 and 4|. It is further assumed that for some unforeseen reason the resistance offered to the broaching tools by the work piece i greater than the power developed in the cylinder 4|. This causes the machine to stall.

In order to correct this condition with a minimum amount of damage to the breaching tools and the other component parts,-it is best to pull the broaches up out of the work piece without releasing the work piece from its clamped position and then move the work holding fixture out of the cutting position into loading position in order to enable the operator to correct the faulty condition. This is accomplished automatically by moving the hand lever I 9| into the extreme right position. Figure 4 of the drawings shows the p0 sition of the parts when the lever I9| is shifted to its reversing position at a time when the. cylinder 4| is moving down. The valves 63 and I have notchanged from the position of Figure 1 but the spool I31 in valve I35 has been shifted to its extreme right hand position. This causes fluid under pressure to flow from lines 46 and 62 into port 14, thence to port 15, line 3 to port I32; From the port I32 the fluid will flow axially to port I3I, thence to line I34 which leads to port I46. From port I46 to the port I41, thence through lines I49 and I50 to the right hand end of the main control valve I6, thereby shifting the spool I8 to the left, the fluid being vented from the left end of the valve I6 through line I 5| to port I45, port I44, line I33, port I29, port I30, line I12, port I69, line I13, to fluid return line 89, and thence to reservoir 8.

This positioning of the valves causes fluid from the pump 5 to pass through the main circuit line 38 to the under side of the piston 38A, thereby reversing the motion of the cylinder 40, and mov-- ing it down to the position from which it started. As heretofore described, this will cause the cylinder 4| to move upwardly towards its top position, from whence it started. During this motion of the cylinders 40 and 4|, the valves 65 and 54 are in their mid-position, and fluid from the lines 46 and 64 is blocked from leaving the four way valve 65 through the ports I06 and I08. This makes ineflfective at this time any movement of the spool I84, as caused by hand lever I 9|. The position of the cylinder 58 will be maintained until the cylinders 48 and 4| have returned to their starting position, as shown in Fig. 1 of the drawmgs, thereby shifting the spools in valves 65 and I54 out of their mid-positions into the position shown in Fig. l and allowing fluid to flow from port I01 to port I86, line I52, port I61, port I66, line I80, to port 193. Due to the reverse posivalve I, thereby shifting the spool in the valve to the opposite or left position and causing fluidfrom the line 50 to flow through line 53, hollow piston rod 51, to the left hand side of the piston BI, thereby causing the cylinder 58 to move tothe left and thereby moving the fixture in question out of the cutting position and into the loading position.

The cylinder 58, upon leaving the position shown in Fig. 4, permits the spring centering device 19 to move the spool 81 in valve 63 to its mid-position. Movement of the valve to midposition causes lines I50 and :I5I leading to valve I6 to be connected to the reservoir 8 through line I5I, port I45, port I44, line I33, port I29, port- I30, line I12, port I69, line I13, line 89, and line 55. The line I50 is vented through port I41, port I48, line I34, port I3I, port I32, line II3, port 15, slots 10A, lines 88, 88, and 55 to reservoir 8. The spool I8 will move to its mid-position, thereby locking cylinders 40 and 4| and venting the pump 5 back to the reservoir. This helps to keep the hydraulic system at low temperature.

Upon reaching its lefthand position, the cylinder 58, by engagement of the lug. 86 with lever 84, shifts the rod 83, lever 18, and rod 11 to move the spool -61 into its left hand position. This movement of the spool does not affect the venting of the main control valve through the line I5I, as described above, because venting from that line does not pass through the valve 83. Also, the line I50 continues to be vented through the valve 83, the land 10 now being moved entirely clear of the port .15. Therefore, no further movement will take place and the cylinders 40, M, and 58 will come to rest and give the operator an opportunity to make correction of whatever was the cause of the stalling of the machine.

After the fault has been corrected, and in order to lead the machine back into its normal operating cycle, the hand lever I9I is moved to the left to the position shown in full lines in Fig. 1, and which position may be marked Go. As heretofore stated, both ends of the main control valve I6, through the lines I50 and I5I, are connected to thereservoir 8, and shifting of the spool I31 does not have any immediate effect.

The four way valve 5I, however, is under control pressure of the line 203, and upon shifting the spool I84 with the handle I9I, this control fluid is switched to the opposite line 202, thereby shifting the spool in the valve 5I and reversing the flow of fluid from the pump 8 to cause the work moving cylinder 58 to move to the right. This is the position shown in Fig. 1, and the hydraulic action will take place, as described before, as the machine is now again on its regular cycle.

Another case has to be provided for, and that is where the operator loads a work piece in the wrong manner which would cause damage if the machine were allowed to proceed with its cycle. If the operator wishes to return the work moving cylinder 58 to its starting position after it hasv left the starting position but before movement of the cylinders 40 and 4| has begun, he again puts the hand lever IOI in the reverse position. The hydraulic condition thereby created is identical with the one heretofore described. The cylinder 58 will reverse and go back where it came from, and'no further movement will take place, the. cylinders 40 and H being locked against movement during this time. Upon making correction on the loading of the work piece, the hand lever I9I may be moved into the go position, and the movements take place in the same manner as heretofore described for the regular and normal cycle of operation of the machine.

The construction and arrangement herein shown and described permits an operator by manipulating thehandle IBI to move any one of, the three hydraulic cylinders in extremely small increments, generally referred to as an inching process. That is to say, the moving parts can be stopped in very short distances and moved very short distances, which is of considerable advantage in setting up a machine incorporating this hydraulic circuit for locating the parts in exact position as is so often wanted.

In order to more readily comprehend the meaning of the claims, the following is a summary of the main features. The pump 5 is referred to as a primary pump; the primary circuit comprises the lines 38 and 39; the primary valve is the pressure operated control valve generally designated I8; and the primary pilot circuit comprises the lines I50, I5I, I33, I34, H2 and H3. The pump 8 is referred to as the secondary pump; the secondary circuit comprises the lines 52 and 53; the secondary valve .is the four way fluid pressure operated valve 5|; and the secondary pilot circuit comprises the lines MI, 202, 203, I80, I8I, I52 and I53. The prefill circuit comprises the lines I14 and I11, and the closed circuit comprises the lines I16 and H8.

Formal changes may be made in the specific embodiment of the invention disclosed without departing from the spirit and substance of the broad invention, the scope of which is commensurate with the appended claims.

What is claimed is:

1. In a; hydraulic circuit, a primary circuit, a pair of work performing hydraulic cylinders having one end of each connected in said primary circuit, a valve for controlling said primary circuit so as to move said cylinders simultaneously in opposite directions,a secondary circuit,a work moving hydraulic cylinder connected in said secondary circuit, a single closed circuit interconnecting the opposite ends of said work performing hydraulic cylinders during movement of either cylinder on its work performing stroke, means for blocking said closed circuit to prevent movement of said work performing cylinders during movement of said work moving cylinder, and means for supplying fluid under pressure to all of said circuits.

2. In a hydraulic circuit having a continuous cycle of operation, a primary circuit, a pair of work performing hydraulic cylinders connected in said primary circuit, a closed circuit connecting said cylinders for moving either one of said cylinders when the other is moved by fluid pressure from said primary circuit, means for prefilling said closed circuit, interlocking means for preventing'operation of said cylinders on contin- 5 secondary circuit, a secondary valve for controlling the flow of fluid to said work moving cylinder, a secondary pilot circuit connected to said secondary control valve for actuating the same, a control valve actuated by said work moving cylinder for controlling the flow of fluid to said primary pilot circuit, a. control valve actuated by inders are moved simultaneously in opposite disaid work performing cylinders for controlling the flow of fluid to said secondary pilot circuit, and means for supplying fluid under pressure to the circuits whereby said work performing cylrections each time after said work moving cylinder is reciprocated to one of its limits.

4. In a hydraulic circuit, a primary circuit, a pair. of work performing hydraulic cylinders in said primary circuit, a primary valve for said primary circuit, a. primary pilot circuit for movingsaid primary valve, a secondary circuit, a work moving hydraulic cylinder in said secondary circuit, asecondary valve for controlling said secondary circuit, a secondary pilot circuit for operating said secondary circuit valve, a valve actuated by said work moving cylinder for controlling. said primary pilot circuit, a valve actu- 'ated by said work performing cylinders for controlling said secondary pilot circuit, and means for supplying fluid under pressure to said circuits.

5. In a hydraulic circuit, a primary circuit, a pair of workperforming hydraulic cylinders in said primary circuit, a primary valve for said primary circuit, a primary pilot circuit for moving said primary control valve, a secondary circuit, a work moving hydraulic cylinder in said primary circuit, a primary pflot circuit for mov-' ing said primary control valve, a secondary circuit, a work moving hydraulic cylinder in said 1 secondary circuit, a secondary valve for controlling said secondary circuit a secondary pilot circuit for operating said secondary circuit valve, a valve actuated by said work performing cylinders for controlling said secondary pilot circuit, a valve actuated by said work moving cylinder for controlling said primary pflot circuit, a closed circuit connected to said work performing cylinders for moving either one of said work performing cylinders when the other is moved by said primary circuit, and means for supplying fluid under pressure to said circuits. l

7. In a hydraulic circuit, a primary circuit, a

. pair of work performing hydraulic cylinders in said primary circuit, a primary valve for said primary circuit, a primary pilot circuit for moving said primary control valve, a secondary circuit, a work moving hydraulic cylinder in said secondary circuit, a secondary valve for controlling said secondary circuit, a secondary pilot circuit for operating said secondary circuit valve, a valve actuated by said work performing cylinders for controlling said secondary pilot circuit, a valve actuated by said work moving cylinder for controlling 'said primary pilot circuit, a closed inders for moving either one of saidwork performing cylinders when the other is moved by said primary circuit, means for supplying fluid under pressure to said circuits, and manually operable valves for controlling both of said pilot circuits.

8. In a hydraulic circuit, a primary circuit, a pair of work performing hydraulic cylinders in said primary circuit, a primary valve for saidprimary circuit, a primary pilot circuit for moving said primary control valve, a secondary circuit, a work moving hydraulic cylinder in said secondary circuit, a secondary valve for controlling said secondary circuit,

-a secondary pilot circuit for operating said secondary circuit valve, a valve actuated by' said work performing cylinders for controlling said secondary pflot circuit, a valve actuated by said work moving cylinder for controlling said primary pilot circuit, a closed circuit connected to said work performing cylinders for moving either one of said work performing cylinders when the other is moved by said primary circuit, means for prefilling said closed circuit, a valve actuated by said work performing cylinders "for controlling such prefill, and means for supplyin fluid under pressure to said circuits.

9. In a hydraulic 'circuit, a primary circuit, a

pair of work performing hydraulic cylinders in said primary circuit, a primary valve for said primary circuit, a primary pilot circuit for moving said primary control valve, a secondary circuit, a work moving hydraulic cylinder in said secondary circuit, a secondary valve for controlling said secondary circuit, a secondary pilot circuit for operating said secondary circuit valve, a valve actuated by said work performing cylinders for controlling said secondary pilot circuit, a valve actuated by said work moving cylinder for controlling said primary pilot circuit, a closed circuit connected to said work p'erforming cylinders for moving either one of said work performing cylinders when theother is moved by said primary circuit, means for prefilling said closed circuit, a valve actuated by said work performing cylinders for controlling such preflll, means for supplying fluid under pressure to said circuits, andmanually operable valves for controlling both of said pilot circuits.

10. In a hydraulic broaching machine, a pair of broaching cylinders, a normally closed circuit connecting one end of each of said broaching cyl inders, means for supplying fluid under pressure alternatively to the opposite endsof said broach- "ing cylinders to effect a' simultaneousbroaching other cylinder followed by a simultaneous return stroke of said one cylinder and a broaching stroke of said other cylinder, means acting automatically between the completion of a broaching stroke of one of the cylinders and the institution of the circuit connected to said work performing cylbroaching stroke of the other'cylinder to feed a" workpiece into position to be broached by said and means acting last mentioned cylinder, throughout the period between the completion of the broaching stroke of one of the cylinders and the institution of the broaching stroke of the other cylinder to apply fluid under pressure to the' closed circuit end of the last mentioned cylinder.

11. In a hydraulic broaching machine, a pair of broaching cylinders, a normally closed cir-- cult connecting one end of each of said broaching cylinders, means for supplyingfluid under said broaching cylinders to effect a simultaneous broaching stroke of one cylinder and a return stroke of the other cylinder followed by a simultaneous return stroke of said one cylinder and. a broaching stroke of said other cylinder, means acting automatically between the completion of a broaching of one of the.cylinders and the institution of the broaching stroke of the other cylinder to feed a workpiece into position to be broached by said last mentioned cylinder, means for blocking said normally closed circuit at a point between said cylinders throughout the period between the completion of a broaching stroke of one of the cylinders and the institution of a broaching stroke of the other cylinder, and means for applying fluid under pressure to theclosed circuit end of the last mentioned cylinder throughout said period to effect a prefill of said normally closed circuit.

12. In a hydraulic broaching machine, a pair of broaching cylinders, means for alternatively supplying pressure fluid to said broaching cylinders at one end of each for moving the cylinders through their broaching strokes, a closed circuit normally connecting the opposite ends of said broaching cylinders to effect return of one cylinder during the broaching stroke of the other, a work moving cylinder adapted at each extremity of its stroke to present work in position to be broached by one of said broaching cylinders, means operable when said broaching cylinders have completed a stroke for reversing the position of said work moving cylinder, means acting on completion of one stroke of said broaching cylinders to prevent a reverse stroke of the broaching cylinders until the work cylinder has completed its movement, means for blocking said normally closed circuit at a point between said cylinders throughout the period between the completion of the broaching stroke of one cylinder and the institution of the succeeding broaching stroke of the other cylinder, and means for connecting said last mentioned cylinder, to a source of pressure throughout said period to effect a prefill of said closed circuit.

13. In a hydraulic broaching machine, a broaching cylinder adapted to reciprocate through a broaching stroke and a return stroke, a work moving cylinder adapted to shift a workpiece into and out of broaching position, means for supplyin fluid under pressure. to said work moving cylinder to shift the same from a starting position in which the workpiece is retracted from said broaching position into a position in which the workpiece is in broaching position, means operable automatically upon completion of the movement of the workpiece into broaching position for supplying fluid under pressure.

to said broaching cylinder to shift the same from a starting position through the broach-'- ing stroke, and manually controlled means operable at any time during the aforesaid movements of said cylinders for automatically returning both of said cylinders to their starting positions in reverse order and direction to the order and direction in which they left said starting positions.

14. In a hydraulic broaching machine, a broaching cylinder adapted to reciprocate through a broaching stroke and a return stroke; a work moving cylinder adapted to move a workpiece-into and out of position to be broached; a hydraulic circuit for said cylinders; circuit control means for continuously operating said cylinders through a cycle from a starting position in which the work moving cylinder has shifted the work out of broaching position and the broaching cylinder is in position to begin the broaching stroke to effect the successive steps of advancing the work to broaching position, broaching the work, and returning the work and the broach to starting position, and manually controlled means operable at any time during the work advancing movement and the broaching stroke to cause the cylinders to be returned from the position they then occupy to the starting position in reverse order and direction to the order and direction in which they last left said starting position.

15. In a hydraulic broaching machine, a broaching cylinder adapted to reciprocate through a broaching stroke and a return stroke; a work moving cylinder adapted to move a workpiece into and out of position to be broached; a hydraulic circuit for said cylinders; circuit control means for continuously operating said.

cylinders through a cycle from a starting position in which the work moving cylinder has shifted the work out of broaching position and the broaching cylinder is in position to begin the broaching stroke to efiect the successive steps of advancing the work to broaching position, broaching the work, and returning the work and the broach to starting position, and manually controlled means operable when actuated durin the broaching stroke to first reverse the broaching cylinder and return it to starting position and then return the work moving cylinder to starting position.

16. In a hydraulic broaching machine; broaching cylinder adapted to through a broaching stroke and a return stroke; a work moving cylinder adapted to move a workpiece into and out of position to be broached; a hydraulic circuit for said cylinders; circuit control means for continuously operating said cylinders through a cycle from a starting position in which the work moving cylinder has shifted the work out of broaching position and the broaching cylinder is in position to begin the broaching stroke to efiect the successive steps of advancing the work to broaching position, broaching the work, and returning the work and the broach to starting position, and manually controlled means operable when actuated during movement of the work moving cylinder in a direction to place the workpiece in broaching position to reverse the direction of motion of the work moving cylinder and return it to starting position.

17. In a hydraulic broaching machine, a pair of broaching cylinders, means for reciprocating said broaching cylinders simultaneously in opposite directions, a work moving cylinder adapted on reciprocation to moving work alternatively into working position with respect to said broach operating cylinders, fluid pressure means for automatically shifting said work moving cylinder to one end of its stroke between successive broaching strokes of the broaching cylinders to shift a workpiece into position to be broached by the cylinder next making its broaching stroke, and manually controlled means operable at any time to cause reverse and return the broaching cylinders to the ends of their strokes if they are intermediate the ends of their strokes and thereafter reverse the position of the work moving cylinder.

18. In a hydraulic broaching machine, a pair reciprocate I of broaching cylinders, means including a primary valve for effecting simultaneous reciprocation of said broaching cylinders in opposite directions, 2. work moving cylinder adapted on reciprocation to move workpieces alternatively into broaching position with respect to said cylinders, means including a secondary valve for reciprocating said work moving cylinder, 3, primary -pilot circuit for actuating said primary valve, a secondary pilot circuit for actuating said secondary valve, a valve in said primary pilot circuit operable'by and upon completion of a stroke of the work moving cylinder to shift the primary valve and effect a broaching stroke of the broaching cylinder into relation with which the workpiece was moved and a return stroke of the other broaching cylinder, a valve in said secondary pilot circuit operable by and upon completion of a stroke of one of said broaching cylinders to effect a shift of the secondary valve and a reversal of the position of the work moving cylinder.

19. In a hydraulic broaching machine, a pair of breaching cylinders, means including a primary valve for effecting simultaneous reciprocation of said broaching cylinders in opposite directions, a work moving cylinder adapted on reciprocation to move workpieces alternatively into broaching position with respect to said cylinders, means including a secondary valve for reciprocating said work moving cylinder, a primary pilot circuit for actuating said primary valve, a secondary pilot circuit for actuating said secondary valve, a valve in said primary pilot circuit operable by and upon completion of a stroke of the work moving cylinder to shift the primary valve and effect a broaching stroke of the broaching cylinder into relation with which the workpiece was moved and a return stroke of the other broaching cylinder, a valve in said secondary pilot circuit operable by and upon completion of the broaching stroke of one of said broaching cylinders and a. return stroke of the other to efiect a shift of the secondary valve and a movement of a workpiece into broaching position with respect to the other broaching cylinder.

20. In a hydraulic broaching machine, a pair of broaching cylinders, means including a primary valve for effecting simultaneous reciprocation of said broaching cylinders in opposite directions, a work moving cylinder adapted on reciprocation to move workpieces alternatively into broaching position with respect to said cylinders, means including a secondary valve forreciprocating said work moving cylinder, 9. primary pilot circuit for actuating said primary valve, a secondary pilot circuit for actuating said secondary valve, a valve in said primary pilot circuit operable by and upon completion of a stroke of th work moving cylinder to shift the primary valve and ellect a broaching stroke of the broaching cylinder into relation with which the workpiece was moved and a return stroke of the other broaching cylinder, a valve in said secondary pilot circuit operable by and upon completion of a broaching stroke of one of said broaching cylinders to eifect a shift of the secondary valve and a movement of a workpiece into broaching position with respect to the other broaching cylinder, and manually controlled means for reversing both pilot circuits to shift both the primary and. secondary valve and efiect automatic sequential. re versal of said cylinders in reverse order to their previous order of movement.

' BENEDICT WELTE.

clanng c m 0F CORRECTION. Petent Ho. 2,256,552. September 16, 19th.-

BENEDICT wELTE.

It is hereby certified that error afipears in the printed specification of the above numbered patent requiring correction as follows: Page 10, first column, line 7, claimfi, strike out the syllable, words, and syllable "index-s are moved simultaneously in opposite di" and insert the same" after May]:- in line 11, same claim; and that the said Letters 'Patent shouldbe-read with this cerrection therein that the semis may confonh to the record of the case in the Patent Office. 7 I I Signed and sealed this 28th of October, A, D.

Henfy. 'Van Arsdale, (3881) Acting Commissioner of Patents. 

